Organic matter of soil

Organic matter

Most soil organic matter accumulates within the surface layer of the soil. This organic matter may be divided into two groups: non-humic matter and humic matter.

Non-humic matter includes all undecomposed organic material within the soil. Examples of non-humic matter are twigs, roots, and living organisms.

Humic matter includes humic acids, fulvic acids, and humin. (Humin is the dark material in soil that is highly resistant to decomposition.)

IMPORTANCE OF SOIL ORGANIC MATTER

• Due to its tremendous surface area, soil organic matter:

• Acts like a sponge to store water
• Retains and provides nutrients (CEC)
• Glues and binds soil particles into stable aggregates

• Reduces the occurrence of aluminum toxicities.

Like low activity clays, organic matter may have either CEC or AEC, depending upon soil pH. However, it will rarely have AEC. In fact, the pH must fall to approximately 2.0 before it will have AEC.

CATION EXCHANGE CAPACITY OR ANION EXCHANGE CAPACITY?

• Soil organic matter may have both AEC and CEC. However, the charges on organic matter are dependent upon soil pH. For soil organic matter to generate an AEC, the soil pH must be 2.0.

MANAGEMENT

Without additions of organic matter, tillage practices will greatly reduce organic matter content in the soil. And so, no-till and minimum tillage systems with the return of organic matter to the soil are gaining favor by farmers to improve and conserve soil quality.